193 lines
7.1 KiB
C++
193 lines
7.1 KiB
C++
/*
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* Copyright (c) 2019, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_OOPS_COMPRESSEDOOPS_HPP
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#define SHARE_OOPS_COMPRESSEDOOPS_HPP
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#include "memory/allocation.hpp"
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#include "memory/memRegion.hpp"
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#include "oops/oopsHierarchy.hpp"
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#include "utilities/globalDefinitions.hpp"
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#include <type_traits>
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class outputStream;
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class ReservedHeapSpace;
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struct NarrowPtrStruct {
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// Base address for oop-within-java-object materialization.
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// NULL if using wide oops or zero based narrow oops.
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address _base;
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// Number of shift bits for encoding/decoding narrow ptrs.
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// 0 if using wide ptrs or zero based unscaled narrow ptrs,
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// LogMinObjAlignmentInBytes/LogKlassAlignmentInBytes otherwise.
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int _shift;
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// Generate code with implicit null checks for narrow ptrs.
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bool _use_implicit_null_checks;
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};
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class CompressedOops : public AllStatic {
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friend class VMStructs;
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// For UseCompressedOops.
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static NarrowPtrStruct _narrow_oop;
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// The address range of the heap
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static MemRegion _heap_address_range;
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public:
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// For UseCompressedOops
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// Narrow Oop encoding mode:
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// 0 - Use 32-bits oops without encoding when
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// NarrowOopHeapBaseMin + heap_size < 4Gb
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// 1 - Use zero based compressed oops with encoding when
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// NarrowOopHeapBaseMin + heap_size < 32Gb
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// 2 - Use compressed oops with disjoint heap base if
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// base is 32G-aligned and base > 0. This allows certain
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// optimizations in encoding/decoding.
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// Disjoint: Bits used in base are disjoint from bits used
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// for oops ==> oop = (cOop << 3) | base. One can disjoint
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// the bits of an oop into base and compressed oop.
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// 3 - Use compressed oops with heap base + encoding.
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enum Mode {
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UnscaledNarrowOop = 0,
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ZeroBasedNarrowOop = 1,
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DisjointBaseNarrowOop = 2,
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HeapBasedNarrowOop = 3,
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AnyNarrowOopMode = 4
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};
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// The representation type for narrowOop is assumed to be uint32_t.
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static_assert(std::is_same<uint32_t, std::underlying_type_t<narrowOop>>::value,
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"narrowOop has unexpected representation type");
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static void initialize(const ReservedHeapSpace& heap_space);
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static void set_base(address base);
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static void set_shift(int shift);
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static void set_use_implicit_null_checks(bool use);
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static address base() { return _narrow_oop._base; }
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static address begin() { return (address)_heap_address_range.start(); }
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static address end() { return (address)_heap_address_range.end(); }
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static bool is_base(void* addr) { return (base() == (address)addr); }
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static int shift() { return _narrow_oop._shift; }
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static bool use_implicit_null_checks() { return _narrow_oop._use_implicit_null_checks; }
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static address* ptrs_base_addr() { return &_narrow_oop._base; }
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static address ptrs_base() { return _narrow_oop._base; }
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static bool is_in(void* addr);
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static bool is_in(MemRegion mr);
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static Mode mode();
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static const char* mode_to_string(Mode mode);
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// Test whether bits of addr and possible offsets into the heap overlap.
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static bool is_disjoint_heap_base_address(address addr);
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// Check for disjoint base compressed oops.
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static bool base_disjoint();
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// Check for real heapbased compressed oops.
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// We must subtract the base as the bits overlap.
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// If we negate above function, we also get unscaled and zerobased.
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static bool base_overlaps();
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static void print_mode(outputStream* st);
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static bool is_null(oop v) { return v == NULL; }
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static bool is_null(narrowOop v) { return v == narrowOop::null; }
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static inline oop decode_raw_not_null(narrowOop v);
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static inline oop decode_raw(narrowOop v);
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static inline oop decode_not_null(narrowOop v);
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static inline oop decode(narrowOop v);
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static inline narrowOop encode_not_null(oop v);
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static inline narrowOop encode(oop v);
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// No conversions needed for these overloads
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static inline oop decode_not_null(oop v);
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static inline oop decode(oop v);
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static inline narrowOop encode_not_null(narrowOop v);
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static inline narrowOop encode(narrowOop v);
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static inline uint32_t narrow_oop_value(oop o);
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static inline uint32_t narrow_oop_value(narrowOop o);
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template<typename T>
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static inline narrowOop narrow_oop_cast(T i);
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};
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// For UseCompressedClassPointers.
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class CompressedKlassPointers : public AllStatic {
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friend class VMStructs;
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static NarrowPtrStruct _narrow_klass;
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// Together with base, this defines the address range within which Klass
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// structures will be located: [base, base+range). While the maximal
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// possible encoding range is 4|32G for shift 0|3, if we know beforehand
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// the expected range of Klass* pointers will be smaller, a platform
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// could use this info to optimize encoding.
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static size_t _range;
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static void set_base(address base);
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static void set_range(size_t range);
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public:
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static void set_shift(int shift);
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// Given an address p, return true if p can be used as an encoding base.
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// (Some platforms have restrictions of what constitutes a valid base
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// address).
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static bool is_valid_base(address p);
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// Given an address range [addr, addr+len) which the encoding is supposed to
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// cover, choose base, shift and range.
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// The address range is the expected range of uncompressed Klass pointers we
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// will encounter (and the implicit promise that there will be no Klass
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// structures outside this range).
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static void initialize(address addr, size_t len);
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static void print_mode(outputStream* st);
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static address base() { return _narrow_klass._base; }
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static size_t range() { return _range; }
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static int shift() { return _narrow_klass._shift; }
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static bool is_null(Klass* v) { return v == NULL; }
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static bool is_null(narrowKlass v) { return v == 0; }
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static inline Klass* decode_raw(narrowKlass v);
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static inline Klass* decode_not_null(narrowKlass v);
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static inline Klass* decode(narrowKlass v);
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static inline narrowKlass encode_not_null(Klass* v);
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static inline narrowKlass encode(Klass* v);
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};
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#endif // SHARE_OOPS_COMPRESSEDOOPS_HPP
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